If you ever need a lesson in stacking vocals, you can get it from The Cars and producer Roy Thomas Baker, with a great example being this week's isolated vocal track of "Let The Good Times Roll" from the band's first 1978 album.
The entire album was recorded in only two weeks, but the background vocals are special in that they fully utilize Baker's unique Stephens 40 track tape machine with layers of overdubs.
This technique has been used a lot since then, but mostly when you have a band that doesn't sing well together. By doubling, tripling, quadrupling (and more) each vocal part, you even out any of the rough parts that might occur while providing a big choir-like sound at the same time. Here's what to listen for (it starts at 0:12);
1. The reverb on the lead vocal is delayed and very long and dark. If fact, it seems to build after the vocal phrase, almost like it was compressed with short release time.
2. Listen to the phrase releases on the harmonies of "Let the good times roll." They're very short, clean and concise.
3. The lead vocal by Ric Ocasek isn't doubled, which is unusual for the time, and it's not exactly in tune, although it's quirky enough that it doesn't matter in the track.